1. Field of the Invention
The present invention generally relates to the field of lifts. More particularly, the present invention relates to lift systems for incline lift applications, such as incline platform lifts, in which a frame or chassis member is supported by guide rollers and movable along a track having a pair of parallel tubular guide rails.
2. Description of the Prior Art
Specifically, one known type of an incline lift system is disclosed in U.S. Pat. No. 5,572,930 issued to Hein on Nov. 12, 1996 for "Elevator System", which discloses a lift for incline or vertical operation. The elevator system comprises a pair of rollers which are rotated about the guide rail to produce the friction force. One of the many disadvantage with the prior art system is that all friction is generated by a single compression spring, which if damaged or removed would result in a partial or complete loss of friction. Another disadvantage with the prior art system is that increase load on the traveling unit has a negative effect on friction requiring static friction force to compensate for the load. A further disadvantage of the prior art system is that a third support rail is required for added stability as the travel path approaches and/or achieves horizontal. In addition, over-moulding of the rollers with polyurethane has been done in such a manner that the rollers squeak during travel and wear out very quickly at the outer edges. A still further disadvantage of the prior art incline lift system is that the use of swivel plates to rotatably drive the rollers into the guide rail which causes the main support axis of the carriage to be offset from the drive axis in such a way that the structural support of the carriage and load is flexible as the swivel plates rotate (i.e: not a positive mechanical connection).
It is highly desirable to have a very efficient and also very effective design and construction of an incline lift system which eliminates all of the disadvantages mentioned above. It is desirable to provide an incline lift system which allows horizontal and vertical bends as well as being able to ascend and descend at an angle in the same direction of travel. It is also desirable to provide an incline lift system that eliminates the possibility of binding between guide rails as a result of being driven on only the top or bottom guide rail.